Laminate battery with deformation restricting member

ABSTRACT

An electrode terminal  42  is connected to a current collector part  12  of electrodes through a deformation restricting member  3 . Between laminate films  2  and  2 , a space  15  is formed above and below the current collector part  12 . The deformation restricting member  3  is placed close to the inner wall peripheral portion of an outer package including sealing parts  23 , thereby forming a deformation-restricting part  22  to restrict the inward deformation of the laminated films  2 . In a section extending from the inside end of the deformation restricting member  3  to a battery element  1 , the laminated films  2  face the space  15  to allow the deformation of the laminated films  2  in response to the change of internal pressure. At the decrease of internal pressure, the contraction of the laminated films  2  can be localized in the deformation-allowing part  21 , thereby reducing the bending stress on an end portion of the sealing parts  23 . Thus, the laminate type secondary battery and the battery pack thereof can be provided with the effect that the concentration of stress on the bonded part of the laminated films can be suppressed even when the expansion and contraction of the laminated films are repeated in response to the change of internal pressure of the laminated films bonded to hermetically accommodate the battery element.

TECHNICAL FIELD

The present invention relates to a secondary battery to be mounted invehicles and more particularly to a secondary battery with a laminatedfilm having high durability which accommodates a battery element.

BACKGROUND ART

Battery packs disclosed in Patent Documents 1 and 2 are power sourcesfor use in portable information technology devices, such as a cellularphone and a mobile computer. The battery back has such a structure thata power generating element such as lithium ion is accommodated in anouter package made of an aluminum laminated film (a laminated sheet),constituting a secondary battery, and the secondary battery is housed ina plastic outer case (pack case). This configuration is to prevent theoutward expansion or the change of outline of the outer case (pack case)when the outer package expands due to the increased internal pressure ofthe secondary battery.

In Patent Document 1, the flat outer case made of synthetic resin hasopenings on both sides of the case in the direction of thickness andmetal plates are stuck on the sides to cover the openings respective sothat the outward expansion of the battery body is released inside theopenings.

In Patent Document 2, a pack case housing a secondary battery isprovided with space formation parts between the secondary battery andthe case, forming spaces between the inner wall of the case and thesecondary battery. When the outer package made of a laminated sheetexpands due to the generation of gas, the expansion of the outer packageis released inside the space formation part, thereby preventing thechange in the outline of the pack case.

A secondary battery disclosed in Patent Document 3 is a lithiumsecondary battery to be used as a battery for portable electronics orpersonal computers. This battery is adapted to prevent breakage of abattery element covered with a flexible synthetic-resin film.

In the secondary battery disclosed in Patent Document 3, a rigidretainer is placed in contact with the sides of a battery element, andthe outer faces of the battery element are covered with the flexiblesynthetic-resin film. This is to prevent a load on the battery elementduring a process of covering the battery element with thesynthetic-resin film or during use, and thus prevent damages or shortcircuits in the battery element.

The above mentioned prior art documents are as listed below.

-   Patent Document 1: Jpn. unexamined patent publication No.    2001-196035 (paragraphs [0002]-[0008])-   Patent Document 2: Jpn. unexamined patent publication No. 2001-57190    (paragraphs [0002]-[0008])-   Patent Document 3: Jpn. unexamined patent publication No.    2000-195475 (paragraphs [0002]-[0008], [0041])

Patent Documents 1 and 2 mentioned above relate to the battery packcomprising the secondary battery in which the battery element isaccommodated in the outer package such as a laminated film and furtherhoused in the pack case for use. This battery pack, in which the packcase has the openings or the space formation part, may absorb theexpansion of the outer package resulting from the increased internalpressure of the secondary battery so that the pack case does not expandor become deformed when pressed by the expanded outer package.

However, films of the laminated film outer package for accommodating thebattery element are bonded by heat welding or another technique toenclose the battery element. While the film outer package repeatedlyexpands and contracts according to the internal pressure, the supportingpoint for deformation at the expansion and contraction is the bondedpart. Accordingly, bending stress would constantly be concentrated onthe bonded part. In the film bonded part, especially, the stress islikely to be concentrated on a discontinuous portion having a steppedstructure or the like, e.g., a portion through which an electrodeterminal protrudes outside, an explosion-proof working part having lowerbonding strength than the bonded part except for such working part andserving as a safety valve in case of excessive internal pressure, andthe like.

In Patent Documents 1 and 2 mentioned above, the film outer packagefacing the openings or the space formation part could freely expand andcontract. However, there is no disclosure about the position of theopenings or space formation part in the pack case. If these openings orspace formation part exist in the bonded part of the film outer package,the stress resulting from the expansion and contraction will repeatedlybe exerted on the bonded part. If the openings or space formation partexist in the bonded part having discontinuity for the electrodeterminal, the explosion proof working part, or the like, the stressconcentration caused by the expansion and contraction would be furtherincreased. This may cause fatigue failure in the bonded part of thelaminated film.

In aforementioned Patent Document 3, the retainers are placed in contactwith the sides of the battery element inside the synthetic-resin film,so that damages to the battery element can be prevented. However, thereis no disclosure about the relief of stress concentration on the bondedpart of the synthetic-resin film resulting from the expansion andcontraction of the film, and therefore the retainer does not seem toserve to relieve the stress. Thus, the stress when repeatedly appliedmay cause fatigue failure in the film.

The present invention has been made to solve at least one of the aboveproblems and has a purpose to provide a laminate type secondary batteryin which a battery element is accommodated in a sealed outer packagemade of laminated films, the secondary battery being capable ofsuppressing the concentration of stress on a bonded part of thelaminated films even if expansion and contraction are repeated inresponse to the change of internal pressure, and to provide a batterypack thereof.

DISCLOSURE OF INVENTION

To achieve the above purpose, a laminate type secondary batterycomprising: an outer package formed of laminated films having endportions which are at least partly bonded together to form a bondedpart; and a battery element hermetically accommodated in the outerpackage, the battery comprising: a deformation-restricting part whichincludes a deformation restricting member placed close to an inner wallof the outer package including the bonded part to restrict thedeformation of the laminated film resulting from expansion andcontraction of the outer package; and a deformation-allowing part whichis arranged apart from the bonded part and allow the deformation of thelaminated film resulting from the expansion and contraction of the outerpackage.

In the laminate type secondary battery of the present invention, thelaminated film is formed in a bag shape having a bonded part as at leastpart of end portions and serves as an outer package accommodating thebattery element in a sealed state. The deformation restricting member isplaced close to the inner wall of the outer package including the bondedpart. This deformation restricting member restricts deformation of thelaminated film at the expansion and contraction of the outer package.The deformation of the laminated film is allowed in thedeformation-allowing part arranged away from the bonded part.

The bonded part of the laminated films is formed by adhesively joining,heat welding, or other techniques. Accordingly, there are generallydiscontinuity in structure at the boundary between the bonded part and anon-bonded part and discontinuity in bonding condition such as a bondingposition and bonding strength in the bonded part. Thedeformation-allowing part allows the deformation of the laminated filmlocally in an area apart from the bonded part, while the deformationrestricting part restricts the deformation of the laminated film in andaround the bonded part. Thus, the part having the structuraldiscontinuity, such as the bonded part and its surrounding portions, canbe prevented from becoming deformed. Further, the concentration ofbending stress on the structural discontinuous part such as the bondedpart can be relieved. This makes it possible to avoid fatigue failure,e.g., cracks, in the laminated film resulting from the bending stress,thus preventing the occurrence of liquid leakage or the like.

At this time, the bonded part of the laminated film preferably includesan electrode bonded part in which the laminated films are bonded to anelectrode terminal. In the part of the laminated film through which theelectrode terminal protrudes outside, the electrode terminal is bondedto the film. The electrode bonded part, which includes a steppedstructure corresponding to the thickness of the electrode terminal, hasdiscontinuity in structure. The deformation of the laminated filmincluding the electrode bonded part can be restricted and therefore theconcentration of the bending stress on the electrode bonded part can besuppressed.

Further, a current collector part may be provided for connecting eachelectrode of the battery element to the electrode terminal. In thiscase, preferably, the deformation-restricting part is provided in asection extending from the electrode bonded part and including at leastpart of the current collector part, and the deformation-allowing part isprovided in a section extending from the battery element and includingat least part of the current collector part.

In the current collector part, the electrodes extending from the batteryelement are collected toward the electrode terminal, so that a spacewidening toward the electrode terminal may be generated in the outerpackage. When the deformation-allowing part is provided in the sectionextending from the battery element and including at least part of thecurrent collector part and the deformation-restricting part is providedin the section including at least part of the current collector part andthe electrode bonded part. Accordingly, the deformation of the electrodebonded part can be restricted while the laminated film is allowed to bedeformed by use of the space around the current collector part.

Further, the deformation-restricting part may be provided in a sectionextending from the electrode bonded part to the battery element throughthe current collector part. Further, the deformation restricting membermay be provided with at least one of an opening, a cutout part, and arecessed part to form the deformation-allowing part.

Here, the deformation restricting member is preferably made of anelectrically insulating member such as a resinous member. This makes itpossible to prevent electric conduction between electrodes in the outerpackage. For instance, the configuration that the electrodes in thecurrent collector part are covered with the deformation restrictingmember can prevent electric conduction between the electrodes through aninner-layer metal film of the laminated film.

In the case where the battery pack is structured by stacking the abovementioned laminate type secondary batteries, a spacer may be placedbetween adjacent batteries, forming a shock-absorbing space between theadjacent batteries. Accordingly, the deformation of the laminated filmin the deformation-allowing part will not interfere with the nextbattery.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an exploded perspective view showing a structure of a laminatetype secondary battery in an embodiment;

FIG. 2 is a perspective view showing the structure of the laminate typesecondary battery in the embodiment;

FIG. 3 is a sectional view of the battery taken along a line A-A of FIG.2;

FIG. 4A is an explanatory view showing deformation of the laminated filmin response to the change of internal pressure in the embodiment;

FIG. 4B is an explanatory view showing deformation of a laminated filmin response to the change of internal pressure in a comparative example;

FIG. 5 is a view showing a first modification of a deformation-allowingpart;

FIGS. 6A to 6C are views showing concrete examples of a deformationrestricting member used in FIG. 5;

FIG. 7 is a view showing a second modification of thedeformation-allowing part; and

FIG. 8 is a schematic view of a battery pack including the secondarybattery in the embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

A detailed description of a preferred embodiment of a laminate typesecondary battery and a battery pack thereof embodying the presentinvention will now be given referring to the accompanying drawings;FIGS. 1 through 8.

As shown in FIGS. 1 and 2, in the laminate type secondary battery in thepresent embodiment, a battery element 1 is hermetically accommodated inan outer package made of laminated films 2. The battery element 1includes positive electrode plates each of which is made of a metallicfoil in film shape applied with a positive active material over thesurface thereof and negative electrode plates each of which is made of ametallic foil in film shape applied with a negative active material overthe surface thereof so that the positive and negative electrode platesare alternately stacked with separators made of resinous porous film,interposed therebetween.

The battery element 1 has such a configuration that rectangular cellelements are laminated in a multilayer form or long lengths of a cellelement wound in a multilayer form is shaped in a rectangle andlaminated one on top of the other. The rectangular laminated batteryelement 1 includes an active material formation part 13 at the centerthere of and metal-film exposed parts applied with no positive/negativeactive material at both side ends of stripe shape, which form positiveand negative electrodes. The positive/negative electrodes are formed atrespective ends of the cell elements laminated in a multilayer form andbounded into one and connected to a flat positive terminal 41 or a flatnegative terminal 42 for extracting a positive or a negative electrodefrom the battery element 1 as a laminate type secondary battery. Thisbounded areas are current collector parts 11 and 12. The battery element1 is connected to the positive terminal 41 and the negative terminal 42through the electrodes bounded by polarity in the current collectorparts 11 and 12. The battery element 1 is hermetically accommodated inan outer package made of laminated films 2 and 2.

Each of the laminated films 2 and 2 constituted by an external surfacemade of nylon and an internal surface made of polypropylene, laminatedwith an aluminum film interposed therebetween. Each film 2 has a sealingpart 23 at the periphery and is formed in a flat-bottomed cup shapehaving the depth about half the thickness of the battery element 1 tocover the upper or lower rectangular surfaces of the battery element 1.The films 2 and 2 are put together from above and below the batteryelement 1, and the sealing parts 23 are adhesively joined or heat weldedto bond the laminated films 2 and 2 to hermetically accommodate thebattery element 1.

Prior to hermetically accommodating the battery element 1, the positiveand negative electrode terminals 41 and 42 and the current collectorparts 11 and 12 are protected by the deformation restricting members 3and 3. Each deformation restricting member 3 is formed suitable for thewidth and thickness of the battery element 1. The deformationrestricting member 3 is configured in outer convex form and providedwith a slit through which each electrode terminal 41, 42 is allowed toprotrude, and an interior concave part for receiving the connected partof the electrode terminal and each of the current collector parts 11,12, and also the current collector parts 11 and 12.

In the outer package, near the inner wall peripheral portion includingthe sealing parts 23 at which the laminated films 2 and 2 are bondedtogether, the side edges of the laminated battery element 1 are disposedalong edges 1U and 1D with no electrode terminals 41 and 42 and theouter end faces of the deformation restricting members 3 and 3 aredisposed along edges 1R and 1L through which the electrode terminals 41and 42 protrude outside. Thus, the inward deformation of the laminatedfilms 2 and 2 can be prevented at the peripheral portion including thesealing parts 23.

FIG. 3 is a sectional view of the secondary battery taken along a lineA-A of FIG. 2. The electrode terminal 42 is inserted in the deformationrestricting member 3 through the slit thereof and is connected to eachelectrode extending from the edge of the laminated battery element 1through the current collector part 12. The sealing parts 23 of thelaminated films 2 and 2 are bonded to both surfaces of the electrodeterminal 42.

The electrode terminal 42 is positioned at substantially the center in adirection of the thickness of the battery element 1. Accordingly, theelectrodes are collected from the layers to the center and thereconnected to the electrode terminal 42. Spaces 15 and 15 are thereforegenerated above/below the current collector part 12 within the laminatedfilms 2 and 2. The deformation restricting member 3 exists close to theinner wall peripheral portion of the outer package including the sealingparts 23, so that the laminated films 2 are separated from the space 15,forming a deformation-restricting part 22 for restricting inwarddeformation of the laminated films 2.

The width of the deformation-restricting part 22 is determined accordingto the depth of the deformation restricting member 3. In FIG. 3, thedeformation restricting member 3 is disposed in a section from thesealing part 23 to the middle of the space 15 extending to the end ofthe battery element 1, thus forming the deformation-restricting part 22.In a section from the inside end of the deformation restricting member 3to the battery element 1, the laminated films 2 face the space 15 andtherefore be deformable according to the changes of internal pressure.In this section, a deformation-allowing part 21 is provided.

FIG. 4A shows the operations and effects of the deformation-allowingpart 21 and the deformation-restricting part 22 in the presentembodiment, showing comparison with a comparative example shown in FIG.4B.

In the present embodiment shown in FIG. 4A, the space 15 is providedabove and below the current collector part 12. Thedeformation-restricting part 22 is arranged as a section extending fromthe sealing parts 23 to the middle of the space 15, and thedeformation-allowing part 21 is arranged as a section extending from themiddle of the space 15 to the battery element 1. The internal pressureis directly exerted on the laminated films 2 existing in thedeformation-allowing part 21. Therefore, decreasing of the internalpressure will cause the inward contraction of the laminated films 2 inthe deformation-allowing part 21 (as illustrated by “2A” in FIG. 4A). Onthe other hand, the laminated films 2 existing in thedeformation-restricting part 22 continuous from the sealing parts 23 areprevented from contracting. At the decrease of internal pressure,accordingly, the laminated films 2 are allowed to locally contract inthe deformation-allowing part 21. The possible deformation of thelaminated with in the comparative example, thus preventing fatiguefailure of the laminated films 2 such as cracks or the like.Consequently, liquid leakage caused by the cracks can be avoided.

In order to sufficiently restrain the contraction of the laminated film2 at the end portion 24 of the sealing part 23 at the decrease ofinternal pressure, it is effective to determine a clearance between thedeformation restricting member 3 and each laminated film 2 within apredetermined range. If this clearance is determined in a range of 0 mmto about 3 mm, the contraction of the laminated films 2 can berestrained. If about 0.01 mm to about 1 mm, furthermore, the contractionof the laminated films 2 can be restrained more reliably.

On the other hand, the comparative example of FIG. 4B shows the casewhere a deformation restricting member 30 covers the entire space 15.The deformation of the laminated films 2 caused at the increase ofinternal pressure is similar to that in the embodiment shown in FIG. 4A.The laminated films 2 will expand (as illustrated by “2B” in FIG. 4B).At the decrease of internal pressure, to the contrary, the laminatedfilms 2, which has no deformation-allowing part in the comparativeexample, contract in a small space existing between the deformationrestricting member 30 and the sealing parts 23 (as illustrated by “2A”in FIG. 4B). Due to expansion and contraction of the laminated films 2,the bending stress will be applied on the end portions 24 of the sealingparts 23, causing cracks or the like in the film.

In the present embodiment the deformation of the laminated films 2 atthe decrease of internal pressure can be localized. Even where theinternal pressure repeatedly increases and decreases, the bending stresswhich will be applied on the end portions 24 can be reduced as comparedwith in the comparative example, thus preventing fatigue failure of thelaminated films 2 such as cracks or the like. Consequently, liquidleakage caused by the cracks can be avoided.

Modified embodiments of the deformation-allowing part are shown in FIGS.5 to 7. FIG. 5 shows a case of a deformation restricting member 3 x,which has openings 31 x and 31 x at positions apart from the sealingparts 23 to provide a deformation-allowing part 21B. This configurationcan realize the deformation restricting member 3 x having the depth ofthe interior concave part enough to completely cover the space 15extending from the sealing parts 23 to the battery element 1. Thecontraction areas of the laminated films 2 at the decrease of internalpressure are localized in the openings 31 x. Accordingly, the bendingstress on the films 2 at the sealing parts 23 can be reduced. Further,the laminated films 2 are supported by the deformation restrictingmember 3 x, so that the laminated films 2 can be prevented from becomingbroken due to external force including impacts such as drops.

FIGS. 6A to 6C show concrete examples of the deformation restrictingmember 3 x. In FIGS. 6A and 6B, each deformation restricting member 3Ahas openings 31A. The shape of each opening 31A is circular in FIG. 6Aand rectangular in FIG. 6B. Irrespective of each shape, the openings 31Acan serve as the deformation-allowing part.

FIG. 6C, a deformation restricting member 3B has cutouts 31B instead ofopenings. FIG. 6C shows the case where the rectangular cutouts 31B areformed, which also can serve as the deformation-allowing partirrespective of the shape.

FIG. 7 shows a configuration example that the battery elementhermetically accommodated in the laminated films 2 is housed in abattery case 6. In this configuration, the deformation restrictingmember 30 is provided to cover the space 15 existing above and below thecurrent collector part 12 and extending from the sealing parts 23 to thebattery element. Instead of providing the deformation-allowing partutilizing the space 15, the battery case 6 is formed with openings 61and 61 above the rectangular surfaces of the battery element, providingdeformation-allowing parts 21C and 21C. Accordingly, the laminated films2 are allowed to be deformed outwardly in the openings. The expansivedeformation of the laminated films 2 at the increase of internalpressure can be localized in the deformation-allowing parts 21C. Thus,the deformation of the laminated films 2 at the sealing parts can besuppressed at the increase of internal pressure, with the result ofreduction in bending stress thereon.

FIG. 8 is a schematic view showing the arrangement of the aforementionedlaminate type secondary batteries as a battery pack. A spacer 7 isinterposed between adjacent batteries to form a shock-absorbing space 71so that the adjacent batteries have no influence on each other when thelaminated films 2 of each battery are deformed in thedeformation-allowing parts. This is an effective structure in the casewhere, the laminated films 2 for each battery element are allowed toexpand only in the deformation-allowing part at the increase of internalpressure. It is to be noted that the spacer 7 may be provided withopenings or recesses corresponding to the openings 61 shown in FIG. 7.

The laminate type secondary battery has heretofore been used in thefield of household electric appliances and, in recent years,increasingly used for various areas beyond the field of such householdelectric appliances, that is, for an in-vehicle battery for hybridelectric vehicles, pure electric vehicles, or the like, of which urgentdevelopment toward the practical use has been needed. In the field ofvehicles, there is a demand for reliability in severe use environmentsincluding a wider range of ambient temperatures than that in the fieldof household electric appliances. It is thus conceivable that theinternal pressure of the secondary battery may largely change dependingon the ambient temperatures varying in the wider range, leading to thelarge variation width of expansion and contraction of the laminatedfilms. In this view, the laminate type secondary battery in the presentembodiment may be used as the in-vehicle battery. The deformation of thelaminated films such as expansion and contraction can be localized inthe deformation-allowing parts even when the internal pressure changeslargely according to the ambient temperatures varying in a wide range.This makes it possible to prevent the concentration of bending stress onthe sealing parts of the laminated films. Further, the fatigue failureof the laminated films such as cracks can be avoided and thereforeliquid leakage resulting from such cracks can be prevented. The laminatetype secondary battery suitable for use in the field of vehiclesdemanding the reliability in severe use environments including the widerambient temperature range can be provided.

The deformation restricting members 3, 3 x, 3A, 3B, and 30 arepreferably made of materials resistant to electrolyte and electricallyinsulating. Such materials also have to be resistant to the electrolytecontaining ethylene carbonate, diethylene carbonate, or a mixed solutionthereof as a solvent, so that the quality of material can remainunchanged without e.g., swelling. Each of the deformation restrictingmembers 3, 3 x, 3A, 3B, and 30 is placed between the electrode and thelaminated films. It is therefore necessary to take measures to preventthe electrodes from becoming electrically conducted with each otherthrough the metallic film such as the aluminum film forming the middlelayer of the laminated film even when the film forming the internalsurface of the laminated film 2 peels off, exposing the metallic film.It is effective to make the deformation restricting member out of theelectrical insulating materials.

The materials having the above properties may include polypropylene(PP), polyethylene (PE), polyphenylene sulfide (PPS),polytetrafluoroethylene (PTFE), or other resin materials.

In the laminate type secondary battery in the present embodiment and thebattery pack thereof, as explained above in detail, the laminated film 2is provided, at its edge, with the sealing part 23 as one example of abonded part or an electrode bonded part. The sealing parts 23 are bondedtogether or to the electrode terminals 41 and 42, forming the laminatedfilms 2 in a bag shape to serve as the outer package hermeticallyaccommodating the battery element 1. The deformation restricting member3 is placed close to the inner wall of the outer package including thesealing parts 23, providing the deformation-restricting part 22 whichrestricts the deformation of the laminated films 2 due to the expansionand contraction of the outer package. The deformation of the laminatedfilms 2 is allowed in the deformation-allowing part 21 apart from thesealing parts 23.

In general, the laminated film 2 is discontinuous in structure at theboundary between a bonded part formed of the sealing part 23 and anon-bonded part except for the sealing part 23, and further the sealingpart 23 also has discontinuity in bonding state such as bonding positionand bonding strength. Therefore, the deformation-allowing part 21localizes and allows the deformation of the laminated films 2 in aposition apart from the sealing parts 23. The deformation-restrictingpart 22 restricts the deformation of the laminated films 2 at thesealing parts 23. Thus, the deformation of the films 2 at the structuraldiscontinuous portions such as the sealing parts 23 and its surroundingscan be suppressed, whereby reducing the concentration of the bendingstress on the discontinuous portions. This makes it possible to avoidfatigue failure of the laminated films 2 such as cracks resulting fromthe bending stress, preventing the occurrence of liquid leakage or thelike.

The deformation restricting member 3 is placed in the portion of thelaminated films 2 through which the electrode terminal 41 or 42protrudes outside. Thus, the restricting member 3 can restrict thedeformation of the laminated films 2 including the structuraldiscontinuous portion having a stepped portion for the thickness of theelectrode terminal 41 or 42.

Further, the deformation-restricting part 22 is provided in the sectionextending from the sealing parts 23 and including at least part of thecurrent collector part 12. The deformation-allowing part 21 is providedin the section extending from the battery element 1 and including atleast part of the current collector part 12. The deformation of thelaminated films 2 is allowed by utilization of the space 15 existingabove and below the current collector part 12, while the deformation ofthe sealing parts 23 can be restricted. The deformation restrictingmember 3A may have openings 31A or the deformation restricting member 3Bmay have cutouts 31B to provide the deformation-allowing part 21B. Thelaminated films 2 are thus allowed to be deformed inwardly. Thecontraction of the laminated films 2 at the decrease of internalpressure can therefore be localized in the deformation-allowing part 21or 21B.

In the case where the battery element hermetically accommodated in thelaminated films 2 is to be housed in the battery case 6, the batterycase 6 may be formed with openings 61 to provide thedeformation-allowing part 21C. This allows the outward deformation ofthe laminated films 2, thus localizing the expansion of the laminatedfilms 2 at the increase of internal pressure in the deformation-allowingpart 21C.

In the case where the above mentioned laminate type secondary batteriesare stacked to construct the battery pack, the shock-absorbing space 71is provided between adjacent batteries, so that the deformation of thelaminated films 2 in the deformation-allowing part will not causeinterference between the adjacent batteries.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential characteristics thereof.

For instance, in the present embodiment, the explanations are made onthe case where each deformation restricting member 3, 3 x, 3A, 3B, and30 is disposed along the portion of the sealing parts 23 through whichthe electrode terminal 42 protrude outside. The present invention is notlimited thereto and of course is effective if the deformationrestricting member is disposed along the portion of the laminated films2 on which the bending stress tends to concentrate at the expansion andcontraction caused by the increased and decreased internal pressure.

The above explanations are made on the case where the deformationrestricting member 3A or 3B is formed with the openings 31A or thecutouts 31B to provide the deformation-allowing part. However, thedeformation-allowing part does not have to be formed as an open area andmay be formed as a recess in the deformation restricting member.

Moreover, the deformation restricting members 3, 3 x, 3A, 3B, and 30and/or the openings 61 may be appropriately combined to provide aplurality of the deformation-allowing parts 21, 21B, and 21C, therebylocalizing the deformable portions of the laminated films 2.

INDUSTRIAL APPLICABILITY

According to the present invention, it is possible to provide thelaminate type secondary battery, with the battery element hermeticallyaccommodated in the laminated films serving as the outer package,capable of suppressing the deformation of the laminated films includingthe bonded part for airtight accommodation, resulting from the expansionand contraction caused by the change of internal pressure, so that theconcentration of stress on the bonded part of the laminated films can bereduced, and also to provide the battery pack.

1. A laminate type secondary battery comprising: an outer package formedof laminated films having end portions which are at least partly bondedtogether to form a bonded part; a battery element hermeticallyaccommodated in the outer package; a deformation-restricting part whichincludes a deformation restricting member, the deformation-restrictingpart being placed apart from the battery element and close to an innerwall of the outer package including the bonded part to restrict thedeformation of the laminated film resulting from expansion andcontraction of the outer package; and a deformation-allowing part whichis arranged apart from the bonded part and between a portion of thedeformation restricting part and the battery element and which allowsthe deformation of the laminated film resulting from the expansion andcontraction of the outer package; wherein the deformation-allowing partis also arranged between the bonded part and the battery element;wherein the deformation-allowing part is further arranged such that thedeformation-allowing part is located either between thedeformation-restricting part and the battery element, or both betweenthe deformation-restricting part and the battery element and in thedeformation-restricting member and wherein the deformation-restrictingmember is not fixed to the outer package.
 2. The laminate secondarybattery according to claim 1, wherein the bonded part includes anelectrode bonded part in which the laminated films are bonded to anelectrode terminal.
 3. The laminate secondary battery according to claim1 further comprising a current collector part for connecting eachelectrode of the battery element to the electrode terminal, wherein thedeformation-restricting part is provided in a section extending from theelectrode bonded part and including at least part of the currentcollector part.
 4. The laminate secondary battery according to claim 2further comprising a current collector part for connecting eachelectrode of the battery element to the electrode terminal, wherein thedeformation-allowing part is provided in a section extending from thebattery element and including at least part of the current collectorpart.
 5. The laminate secondary battery according to claim 3, whereinthe deformation-restricting part is provided in the section extendingfrom the electrode bonded part to the battery element through thecurrent collector part, and the deformation restricting member isprovided with at least one of an opening, a cutout, and a recess to formthe deformation-allowing part.
 6. The laminate secondary batteryaccording to claim 1, wherein the deformation restricting member is madeof an electrically insulating member.
 7. The laminate type secondarybattery according to claim 1, wherein the deformation restricting memberis made of a resinous member.
 8. The laminate type secondary batteryaccording to claim 1, wherein a distance between the deformationrestricting member and the inner wall of the outer package is preferably0 mm to 3 mm.
 9. The laminate secondary battery according to claim 8,wherein the distance between the deformation restricting member and theinner wall of the outer package is further preferably 0.01 mm to 1 mm.10. A battery pack including the laminate secondary batteries accordingto claim 1 in a stacked relation, comprising: a spacer provided betweenadjacent ones of the batteries to form a shock-absorbing spacetherebetween to prevent interference between the adjacent batteries bythe deformation of the laminated film at the deformation-allowing part.11. The laminate secondary battery according to claim 4, wherein thedeformation-restricting part is provided in the section extending fromthe electrode bonded part to the battery element through the currentcollector part, and the deformation restricting member is provided withat least one of an opening, a cutout, and a recess to form thedeformation-allowing part.